Wouldn't it be great if someday iPhone OS was open sourced so the whole world could learn from it, improve on it...
Well, yes and no. Yes because lots of people would learn. No because the whole point of the platform is the rigidly consistent experience. It's a great portion of the reason why many people purchase it. If Apple does what you say it is no different than Android and then carries the same potential for fragmentation that Android is already seeing.
IMO that's what Android is for. There's an open source offering and a closed (palm and win mobile excluded for this response). You can do whatever you choose. Buy a phone from HTC that is their interpretation of what a smart phone based on android should be. Buy an iPhone. who cares? In either case you're making concessions: Droid is just simply not as cool as an iPhone, it doesn't have the apps (it does have a lot of cool apps, but not nearly the volume or breadth of the the iPhone) and doesn't have the cache that Apple enjoys and is important to some. apple has a great product, lots of apps and a walled garden based on a closed source OS. Take your pick, it's up to you.
I love it. Since Android based phones are clearly available to more people on more platforms than Apple, it is unarguable that Apple is single handily decreasing the capability for people to get to net and the world of information (as you have). Apple is a brilliant option, but only an option. With the Apple cool in your pocket you sacrifice some things. Just as you do with a Droid. It's about what you are willing to concede.